Debugging the Z8

Did everything fire up and work perfectly the first time with this project? Well, in a word, no. Let's see, how did it go?

I mentioned the problems already with the clutch and the driveshaft, but those were solved before I finished bolting it together.

When time came to fire up the motor, I decided to pull the plugs and let the starter turn it over until I got oil pressure. The motor had been sitting for several years. Well, I cranked and cranked and cranked, but to no avail. The starter was cooking hot. Eventually, I discovered that the fuse I had pulled to disable the fuel pump during this (didn't want to run down the battery from the fuel pump) also powered the oil pressure gauge. I put that back in, and all of a sudden the gauge was showing lots of pressure.

It took a while to adjust the turn-on point for the electric fan, I was a little confused about what direction was what with the control (I type with a red face). I might note that with the aggressive cam I have in the car (spec'ed by Comp Cams as "rough idle"), the engine slows down noticeably when the fan goes on when the motor is idling. Meanwhile the ammeter on the dash goes to 45A. If it is correct, that means the fan is about ¾ horsepower – quite the load.

What else – when I took about the third drive, and started to get more aggressive with the Z8, I found that if I nailed it in first or second, but not quite enough to break the tires loose, there was a bad noise coming from the back of the car. I discovered that the big honking U-joint on the back of the driveshaft was whacking away at the emergency brake linkage. I fixed that (and improved the driveshaft geometry) with the spacers that lowered the front of the differential. I described them earlier in the description, but actually added them after I was "done." Speaking of that, I made the first spacers from Delrin since I had some of it in stock and it's nice to machine. But a friend, Jim Froula, stopped by and recommended that aluminum would be better – he's had a bad experience using Delrin in similar applications. Had it been anyone else, I would have stayed with the Delrin. But Jim is a very capable guy and seldom wrong, so I listen to what he says and consequently spent a number of hours redoing them in aluminum. Jim's the type of guy who, for example, doesn't mind ripping out the whole front suspension of a car and designing a better system from scratch. He runs Racecraft, mentioned in the sources section of this.

Also, I noticed that the cooling system was losing some water and that when I revved up the motor, the top radiator hose was collapsing. I replaced the radiator cap, and bought a radiator hose with a spring inside, then put that spring into my top hose. My sympathetic manager at CarQuest felt bad about the $12 spring, but I didn't know where else to get one. Maybe I should have made a junkyard run.

That's about it so far. I still don't have a lot of miles on it. It's a cold wet winter in Seattle, and I can't bear to drive it in the wet yet – everything underneath is so pretty! I'll keep this section updated if I find anything else.

Moving forward a bit now, I've installed motor number two, the Weber version  Here are some new teething issues.

I found that there was some exhaust coming out through the unused Thermactor ports in the heads, so needed to plug them.  I also needed to install richer idle jets to allow the idle screws to be about the right mixture at one or one and a half turns. I've got it so that it idles pretty nicely at about 900 RPM (even with this nasty cam) and there doesn't appear to be any serious carb set-up problems. I plan to replace the emulsion tubes with ones that give a slighter richer mixture at a transition point of the carbs, but this decision is based primarily on web and book research rather than the way it runs.

I had to go back to change the exhaust system for more clearance as it was routed around the differential. When I built the exhaust, I was thinking of how far the exhaust moved only. What I didn't think about was that the differential moves a fair amount too. On the drivers side, the torque of acceleration moves the two together - both moving separately but towards each other.

I'll update this as I get a few more miles on it and find (and hopefully fix) remaining issues.


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